Pleasure releases endorphins in the brain, and to some degree parallel the chemical reactions that characterize illegal drug addiction. All pleasure. That includes writing a good weekly report to your boss, gettin' down with the significant other, consuming a juicy steak, all pleasure. Since we all experience pleasure from one thing or another at sometime in our lives, and since the above biochemical statements made above are generally accepted medical fact, then we are all guilty of having "drug-like" behavior in our brains and since some drugs are illegal the laws regarding unreasonable search and seizure should be suspended because everyone is guilty. The perfect thoughtcrime.
Same reason people addicted to "runners high" will go out an pound their joints to gravel day after day, even after their doctor tells them if they don't quit they're going to end up crippled.